Cohort Profile: The Australian Generating evidence on antimicrobial resistance in the aged care environment (GRACE) study; alignment with national population characteristics

ABSTRACT Purpose The emergence of antibiotic-resistant bacteria represents a considerable threat to human health, particularly for vulnerable populations such as those living in residential aged care. However, antimicrobial resistance (AMR) carriage and modes of transmission remain incompletely understood. The Generating evidence on antimicrobial Resistance in the Aged Care Environment (GRACE) study was established to determine principal risk factors of AMR carriage and transmission in residential aged care facilities (RACF). Participants Between March 2019 and March 2020, 279 participants were recruited from five South Australian RACFs. The median age was 88.6 years, the median period in residence was 681 days, and 71.7% were female. A dementia diagnosis was recorded in 54.5% and more than two thirds had moderate to severe cognitive impairment (68.8%). Sixty-one percent had received at least one course of antibiotics in the 12 months prior to enrolment. Findings to date To investigate the representation of the GRACE cohort to Australians in residential aged care, its characteristics were compared to a subset of the historical cohort of the Registry of Senior Australians (ROSA). This included 142,923 individuals who were permanent residents of RACFs on June 30th, 2017. GRACE and ROSA cohorts were similar in age, sex, and duration of residential care, prevalence of health conditions, and recorded dementia diagnoses. Differences were observed in care requirements and antibiotic exposure (both higher for GRACE participants). GRACE participants had fewer hospital visits compared to the ROSA cohort, and a smaller proportion were prescribed psycholeptic medications. Future plans Participant and built environment metagenomes will be used to determine microbiome and resistome characteristics. Individual and facility risk exposures will be aligned with metagenomic data to identify principal determinants for AMR carriage. Ultimately, this analysis will inform measures aimed at reducing the emergence and spread of antibiotic resistant pathogens in this high-risk population. Strengths and limitations of this study The GRACE study captured a diverse array of data; demographics, medications, personal and medical care, RACF management practices, as well as oropharyngeal, intestinal, and environmental metagenomic data, allowing detailed analysis of exposure-resistome relationships. A high rate of participant recruitment (75% of eligible residents) was achieved, representing the spectrum of resident characteristics and care needs. This included a representative proportion of individuals with moderate or severe cognitive impairment. The main limitation of this cohort resulted from the early cessation of recruitment, due to stringent facility access regulations resulting from the COVID-19 pandemic. While a high recruitment rate partially compensated in terms of cohort size, we were unable to complete recruitment at our fifth site or begin recruitment at two further sites. Ethnic and linguistic data was not captured and so could not be compared between cohorts.